In systemic lupus erythematosus (SLE) the utility of serial anti-dsDNA antibody and complement measurements in clinical decision-making remains controversial. This study proposes two Specific Aims designed to address these issues. In Specific Aim 1 we will take advantage of a unique opportunity to collaborate with a large, multi- center NIH sponsored protocol, the Safety of Estrogens in Systemic Lupus National Assessment (SELENA) trial. We will perform an Observational Study of approximately 1000 women enrolled in the SELENA trial to assess the sensitivity, specificity and predictive value of anti-dsDNA antibodies, C3, C4, CH50, C3a desArg. Using samples obtained from patients enrolled in the SELENA study we will perform subgroup analyses in diverse ethnic groups, patients treated with exogenous estrogen and patients with chronically depressed CH 50. In Specific Aim2, an Interventional Study, we will evaluate the effectiveness of short-term corticosteroid treatment in averting flares when elevations of plasma C3a are accompanied by rising anti-dsDNA antibodies. We will determine whether corticosteroid treatment reduces the frequency of clinical flare, serological abnormalities or disease activity in inactive or stable patients. We will explore whether steroids disproportionately exacerbate or initiate co-morbid medical conditions which may be more prevalent among minority patients (eg., hypertension, diabetes). It is anticipated that the studies proposed will result in observations which lead to rational, cost-effective and evidence-based guidelines which improve the treatment of patients with SLE and by decreasing the morbidity of disease, result in significant improvement of their quality of life.